The objective of the proposed research is to improve our knowledge of the light-scattering properties of the normal and traumatized corneal epithelium. Disturbance of this layer of the cornea can produce significant loss of vision due to increased light-scatter by the cells. This research will investigate transparency changes due to two commonly encountered situations - namely osmotic change and hypoxia. Stromal and epithelial thickness will be monitored, and the results will enable a statement to be made about the thickness/transparency relation in the epithelium. This relation is not well understood for the epithelium, although it has been thoroughly studied in the stroma. Thickness measurements will be made of the epithelium of an excised rabbit cornea using a specular microscope. The addition of a photocell to the eyepiece will allow measurement of back-scattered light at various depths in the epithelium. The solution bathing the cornea will be varied in osmolarity and oxygen concentration, and related to epithelial thickness and light-scattering. This relationship is poorly understood and clarification would be an important contribution to our knowledge of the cornea. The corneal epithelium is the first ocular structure to be exposed to foreign materials such as infection, atmospheric pollutants, accidentally instilled toxic substances, and drugs. Demonstration that epithelial light-scatter varies even with mild forms of trauma could lead to a novel technique for detecting substances potentially hazardous to the cornea.